1. Field of the Invention
This invention pertains to the field of medical equipment and supplies. More particularly, it pertains to the field of dental equipment of the disposable type and, especially to strips of materials known as matrices and dental finishing and polishing devices.
2. Description of the Prior Art
Metal amalgams and foils for tooth restoration are giving way to nonmetals, such as silicates and filled and unfilled acrylic resins, when the restoration is located in the maxillary and mandibular anterior (front) teeth because of the more desirable cosmetic effect. They are also cheaper and take less time to install and are thus also desired in some posterior teeth repair. The nonmetals have poorer physicals and thus are limited to areas of low compression stress, where mastication is not a factor, such as on the proximal surfaces of maxillary lateral incisors.
Routinely, the dentist locates the carious lesion and determines the logical approach and the outline form, then gives the patient a local anesthetic, matches the color of the nonmetal material to the surrounding teeth and roughs in the outline or extension (convenience form) with the appropriate drilling instrument. The site is then isolated with a rubber dam and the cavity walls are prepared to receive the restoration material. A matrix or narrow strip of flexible material is inserted in the interproximal area to insure isolation of the site from the adjacent tooth. The cavity is then washed with an acid solution, rinsed, air dried and a thin coating of a bonding agent applied. The restoration material is then mixed in the proper proportions and inserted into the cavity. The matrix is then pulled over the proximal surface to "round off" and conform the material to the general contour of the tooth and held in place while the material cures by polymerization or other chemical reaction. Some of the modern restoration materials are cured by the incidence of light and so a high intensity light beam is directed through a diaphanous matrix and onto the injected material. It is necessary to slightly overfill the cavity with restorative material to insure absolute filling of the cavity. This excess material oozes from the cavity and forms a "flash" or overhanging lip just under the matrix that cures to a hard state.
After curing is complete, the matrix is removed and a narrow sand paper strip or polishing cloth is inserted edgewise between the teeth and reciprocated or moved back and forth by hand to abrade the overfill and remove the flash. The main problem with this procedure comes from the fact that the matrix is thinner than the sanding strip and the flash and matrix completely fill the interproximal space between the teeth. When the matrix is removed, the flash remains and there is insufficient space to allow insertion of the sanding strip with literally "prying" the teeth apart. It is common therefore that many sanding strips break while trying to insert them into the interproximal area. Sometimes, excessive force is used to insert the strip resulting in the strip being forced past the filled cavity into the gingival region near the base of the teeth causing trauma to the soft gums and hemmorage in the tissue.